JP2013160990A - Optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To expand a scanning range in a main scanning direction.SOLUTION: In an optical scanner 1, a three-degree-of-freedom coupled oscillatory system comprises a mirror 13, an inner gimbal 12, an outer gimbal 11, a support part 3 and elastic connection parts 14 to 16. Therefore, the optical scanner applies voltage between interdigital electrode parts 17 and 19 and interdigital electrode parts 4a and 4b, and operates periodic external force on the outer gimbal 11. A signal for driving the interdigital electrode part 4a is a signal obtained by multiplying a first main scanning drive signal whose voltage at a main scanning frequency changes from a low level of 0 V to a high level higher than the low level and whose duty is 50% by a first subscanning drive signal whose voltage at a subscanning frequency changes from a low level higher than 0 V to a high level higher than the low level and whose duty is 50%. And a signal for driving the interdigital electrode part 4b is a signal obtained by multiplying a signal with a phase of the first main scanning drive signal shifted 180° by a signal with a phase of the first subscanning drive signal shifted 180°.

Description

  The present invention relates to an optical scanning device that scans a light beam.

In recent years, various optical scanning devices using MEMS (Micro Electro Mechanical Systems) technology have been proposed for the purpose of downsizing the optical scanning device.
On the other hand, the applicant of the present application excites two vibration modes by exciting a three-degree-of-freedom torsional vibration system with a piezoelectric bimorph, and torsionally vibrates a mirror disposed in the center in two directions. A two-dimensional optical scanning device configured to perform optical scanning is proposed (see Patent Document 1).

JP-A-7-199099

  In general, in a two-dimensional optical scanning device, it is desired that the scanning range in the main scanning direction oscillating at a high frequency is larger than the scanning range in the sub scanning direction oscillating at a low frequency. However, since the main scanning direction needs to be vibrated at a high frequency, there is a problem that it is difficult to enlarge the scanning range.

  The present invention has been made in view of these problems, and an object of the present invention is to increase the scanning range in the main scanning direction in a two-dimensional optical scanning device.

  In order to achieve the above object, an optical scanning device according to claim 1, further comprising: a reflecting portion having a reflecting surface for reflecting the light beam; and an elastically deformable first elastic connecting portion connected to the reflecting portion. And a first support portion that swingably supports the reflection portion with the first elastic connection portion as a first rotation axis, and a second elastic connection portion that is elastically deformable connected to the first support portion, A second support portion that swingably supports the first support portion with the second elastic connection portion as a second rotation axis, and a third elastic connection portion that is elastically deformable connected to the second support portion; A third support portion that swingably supports the second support portion with the elastic coupling portion as the third rotation axis, and includes a reflection portion, a first support portion, a second support portion, a third support portion, and a first elasticity. The connecting portion, the second elastic connecting portion, and the third elastic connecting portion are torsionally vibrated at a large rotation angle when an inherent periodic external force is applied. Configuring the freedom coupled vibration system.

  For this reason, the optical scanning device according to claim 1 has a degree of freedom of twisting with respect to the first elastic connecting portion, the second elastic connecting portion, and the third elastic connecting portion with the third support portion as a fixed end. It is a torsional vibrator with 3 degrees of freedom.

  A three-degree-of-freedom torsional vibrator theoretically has three vibration modes. That is, the three vibration modes have different resonance frequencies, and the ratios of the angular amplitudes of the torsional vibrations of the reflection part, the first support part, and the second support part with respect to each resonance frequency are different (this is called a vibration mode). . Therefore, when the angular amplitude of the second support portion increases in a certain vibration mode, the angular amplitude of the reflection portion and the first support portion increases according to the ratio of the angular amplitude in the vibration mode.

Then, the external force application means applies a periodic external force unique to the three-degree-of-freedom coupled vibration system. As a result, the torsional vibrator having three degrees of freedom can be brought into a resonance state.
Further, if a periodic excitation force having a frequency corresponding to each of the three vibration modes is given, each vibration mode can be excited. In addition, if a plurality of periodic excitation forces with a plurality of frequencies are superimposed and applied, a plurality of vibration modes can be excited simultaneously.

  Accordingly, the periodic excitation force corresponding to the vibration mode having a large angular amplitude of the reflecting portion and the periodic excitation force corresponding to the vibration mode having a large angular amplitude of the first support portion are superimposed and given. The laser beam reflected by the part can be scanned two-dimensionally.

  The external force acting means includes a first external force acting means that applies a specific periodic external force to one side of both sides of the second support portion sandwiching the third rotation shaft, and a second support portion sandwiching the third rotation shaft. And a second external force acting means for applying a specific periodic external force to the other of the two sides.

  Further, the drive signal generation means for generating a drive signal for driving the external force action means includes a first drive signal for driving the first external force action means and a second drive for driving the second external force action means. Generate a signal.

  The first drive signal is set in advance so that the voltage is higher than the first low level from the first low level that is set in advance so that the voltage becomes 0 V at the main scanning frequency that is the frequency at which the reflecting portion swings. In addition, the first pulse signal that changes to the first high level and has a duty of 50% and the sub-scanning frequency that is the frequency at which the first support portion swings are set in advance so that the voltage is higher than 0V. A signal obtained by multiplying the second pulse signal having a duty of 50% while changing from a second low level to a second high level set in advance so as to be higher than the second low level. This is a signal obtained by multiplying a signal obtained by shifting the phase of the first pulse signal by 180 ° and a signal obtained by shifting the phase of the second pulse signal by 180 °.

  First, the first drive signal and the second drive signal are signals obtained by multiplying a pulse signal that oscillates at the main scanning frequency by a pulse signal that oscillates at the sub-scanning frequency. For this reason, the first external force application means and the second external force application means respectively correspond to vibration modes in which the reflection part vibrates at the main scanning frequency on one side and the other side of the second support part across the third rotation shaft. A periodic excitation force and a periodic excitation force corresponding to a vibration mode in which the first support portion vibrates at the sub-scanning frequency can be applied in a superimposed manner. Thereby, the reflection part vibrates at the main scanning frequency, and the first support part vibrates at the sub-scanning frequency, and the laser beam reflected by the reflection part can be scanned two-dimensionally. In addition, by applying the superimposed periodic excitation force to the second support part, the second support part reciprocally vibrates at the main scanning frequency with the third elastic coupling part as the third rotation axis. Vibrates to swell at the sub-scanning frequency.

  The first drive signal is a signal obtained by multiplying the first pulse signal and the second pulse signal. For this reason, the first drive signal changes from a voltage value of 0 V to a predetermined high level higher than 0 V (hereinafter referred to as a first drive signal high level) at the main scanning frequency.

  On the other hand, the second drive signal is a signal obtained by multiplying a signal obtained by shifting the phase of the first pulse signal by 180 ° and a signal obtained by shifting the phase of the second pulse signal by 180 °. Therefore, the voltage value of the second drive signal becomes a predetermined high level higher than 0V when the voltage of the first drive signal is 0V, and when the voltage of the first drive signal is the first drive signal high level. , 0V.

  Therefore, when the first external force application means applies a periodic excitation force to one side of the second support portion, the second external force application means does not apply a periodic excitation force to the other side of the second support portion. . Similarly, when the second external force application means applies a periodic excitation force to the other side of the second support portion, the first external force application means applies a periodic excitation force to one side of the second support portion. Absent.

  For this reason, the first external force application means and the second external force application means do not apply their own periodic excitation force to the second support portion so as to cancel the other periodic excitation force. Thereby, the vibration amplitude when the second support portion reciprocally vibrates at the main scanning frequency using the third elastic coupling portion as the third rotation axis can be increased. In the three-degree-of-freedom coupled vibration system, the vibration amplitude at which the reflection portion vibrates at the main scanning frequency and the vibration amplitude at which the first support portion vibrates at the sub-scanning frequency are proportional to the vibration amplitude of the second support portion. For this reason, the vibration amplitude at which the reflecting portion vibrates at the main scanning frequency is increased, and the scanning range in the main scanning direction can be increased.

1 is a plan view showing a configuration of an optical scanning device 1. FIG. It is a figure which shows the AA cross section of FIG. It is a figure which shows the BB cross-section part of FIG. 2 is a block diagram showing an electrical configuration of the optical scanning device 1. FIG. It is a timing chart which shows the voltage waveform of a drive signal. It is a figure which shows CC cross-section part of FIG. 4 is a timing chart showing the amplitude of an outer gimbal 11 and voltage waveforms of first and second drive signals.

Embodiments of the present invention will be described below with reference to the drawings.
The optical scanning device 1 is manufactured, for example, by processing an SOI (Silicon On Insulator) wafer by a semiconductor process, and as shown in FIG. 1, a light beam scanning unit 2 that scans a light beam, and a light beam scanning. A support unit 3 that supports the unit 2, a drive unit 4 that applies a rotational driving force to the light beam scanning unit 2, and an angle detection unit 5 that detects a rotation angle of the light beam scanning unit 2.

  The light beam scanning unit 2 includes an outer gimbal 11, an inner gimbal 12, a mirror 13, elastic connecting portions 14a and 14b, elastic connecting portions 15a and 15b, elastic connecting portions 16a and 16b, comb electrode portions 17, 18, 19, 20.

  Among these, the mirror 13 has a circular shape, and a mirror surface portion of an aluminum thin film is formed on the surface. The inner gimbal 12 has a frame shape, and a mirror 13 is disposed in the frame. The outer gimbal 11 has a frame shape, and the inner gimbal 12 is disposed in the frame.

  The elastic connecting portion 16 a is made of an elastically deformable material, and is disposed within the frame of the inner gimbal 12 to connect the mirror 13 and the inner gimbal 12. The elastic connecting portion 16b is made of an elastically deformable material, and is disposed in the frame of the inner gimbal 12. The mirror 13 and the inner gimbal 12 are connected to the opposite side of the elastic connecting portion 16a with the mirror 13 in between. Link. The elastic connecting portion 16 a and the elastic connecting portion 16 b are arranged on the same straight line passing through the center of gravity JS of the mirror 13 and serve as the rotation axis k of the mirror 13. As a result, the mirror 13 is configured to be capable of torsional vibration about the rotation axis k.

  The elastic connecting portion 15 a is made of an elastically deformable material, and is disposed in the frame of the outer gimbal 11 to connect the inner gimbal 12 and the outer gimbal 11. The elastic connecting portion 15b is made of an elastically deformable material, and is arranged in the frame of the outer gimbal 11. The inner gimbal 12 and the outer gimbal 11 are disposed on the opposite side of the inner connecting gimbal 12 from the elastic connecting portion 15a. And The elastic connecting portion 15 a and the elastic connecting portion 15 b are arranged on the same straight line passing through the center of gravity JS of the mirror 13 and the inner gimbal 12 and serve as the rotation axis j of the mirror 13. As a result, the inner gimbal 12 is configured to be capable of torsional vibration about the rotation axis j.

  The elastic connecting portion 14 a is made of an elastically deformable material, and connects the upper side 11 a of the outer gimbal 11 and the support portion 3. The elastic connecting portion 14b is made of an elastically deformable material, and connects the lower side 11b of the outer gimbal 11 and the support portion 3 on the opposite side of the elastic connecting portion 14a across the outer gimbal 11. The elastic coupling portion 14 a and the elastic coupling portion 14 b are arranged on the same straight line passing through the center of gravity JS of the mirror 13, the inner gimbal 12, and the outer gimbal 11, and serve as the rotation axis i of the outer gimbal 11. As a result, the outer gimbal 11 is configured to be torsionally vibrated around the rotation axis i.

  The comb electrode portion 17 is formed in a comb shape along the left side 11 c of the outer gimbal 11. Further, the comb electrode portion 18 is formed in a comb shape along the left side 11 c above the comb electrode portion 17.

  Further, the comb electrode portion 19 is formed in a comb shape along the right side 11 d of the outer gimbal 11. Further, the comb electrode portion 20 is formed in a comb shape along the right side 11 d above the comb electrode portion 19.

  Next, the support portion 3 includes an upper support portion 3a connected to an end portion of the elastic connection portion 14a on the side not connected to the upper side 11a, and an end portion of the elastic connection portion 14b on the side not connected to the lower side 11b. It is comprised from the lower side support part 3b connected.

  Further, the driving unit 4 is formed in a comb-teeth electrode portion 4a formed in a comb-teeth shape that meshes with the comb-teeth electrode unit 17 with a predetermined interval, and in a comb-teeth shape that meshes with the comb-teeth electrode unit 19 with a predetermined interval. And the comb electrode portion 4b.

  Further, the angle detection unit 5 is formed in a comb-teeth shape that is meshed with the comb-teeth electrode unit 18 with a predetermined interval and a comb-teeth shape that is meshed with the comb-teeth electrode unit 20 with a predetermined interval. It is comprised from the comb-tooth electrode part 5b made.

  Further, as shown in FIGS. 2 and 3, each of the comb electrode portions 4a and 4b is one of two surfaces KM1 and KM2 that are not opposed to the comb electrode portions 17 and 19 (FIGS. 2 and 3). Then, a conductive thin film 22 is provided on the surface KM1) with an insulating film 21 interposed therebetween. Similarly, the comb-teeth electrode portions 5a and 5b are also provided with a conductive thin film 22 with an insulating film 21 interposed therebetween.

Next, the electrical configuration of the optical scanning device 1 will be described.
As shown in FIG. 4, the optical scanning device 1 includes a drive signal generation circuit 31, amplification circuits 32 a and 32 b, CV conversion circuits 33 a and 33 b, a semiconductor laser 34, and a control circuit 35.

Among these, the drive signal generation circuit 31 includes a main scan drive signal generation unit 41, a sub scan drive signal generation unit 42, and multipliers 43 and 44.
First, the main scanning drive signal generation unit 41 rotates the light beam scanning unit 2 with a pulse signal whose voltage changes from a low level to a high level at a frequency for scanning the light beam in the main scanning direction (hereinafter referred to as a main scanning frequency). It outputs as a drive signal for driving. Hereinafter, the drive signal output from the main scanning drive signal generation unit 41 is referred to as a main scanning drive signal.

  As shown in FIGS. 4 and 5, the main scanning drive signal generation unit 41 uses the first main driving signal with a voltage ratio of 50% as a main scanning driving signal (hereinafter referred to as duty) as 50%. The scan drive signal MS1 and the second main scan drive signal MS2 whose phase is shifted by 180 ° with respect to the first main scan drive signal MS1 are output. The low level voltage value of the first main scanning drive signal MS1 is 0V.

  The sub-scanning drive signal generation unit 42 rotates the light beam scanning unit 2 with a pulse signal whose voltage changes from a low level to a high level at a frequency at which the light beam is scanned in the sub-scanning direction (hereinafter referred to as a sub-scanning frequency). It outputs as a drive signal for driving. Hereinafter, the drive signal output from the sub-scanning drive signal generation unit 42 is referred to as a sub-scanning drive signal.

  Then, the sub-scanning drive signal generation unit 42 has a first sub-scanning driving signal SS1 having a duty of 50% as a sub-scanning driving signal and a second phase that is 180 ° out of phase with the first sub-scanning driving signal SS1. A sub-scanning drive signal SS2 is output. The low level voltage value of the first sub-scanning drive signal SS1 is higher than 0V.

  Further, as shown in FIG. 4, the multiplier 43 calculates a multiplication value of the first main scanning drive signal MS1 and the first sub-scanning driving signal SS1, and uses a signal indicating the multiplication value as the first driving signal D1. Output (see FIG. 5). Further, the multiplier 44 calculates a multiplication value of the second main scanning drive signal MS2 and the second sub-scanning driving signal SS2, and outputs a signal indicating this multiplication value as the second driving signal D2 (see FIG. 5). .

  The amplifier circuit 32a amplifies the first drive signal D1 output from the multiplier 43 and applies it to the thin film 22 of the comb electrode portion 4a. The amplifier circuit 32b amplifies the second drive signal D2 output from the multiplier 44 and applies it to the thin film 22 of the comb electrode portion 4b.

The CV conversion circuits 33a and 33b convert the electrostatic capacitance between the thin film 22 of the comb electrode portions 5a and 5b and the comb electrode portions 18 and 20 into a voltage value.
The semiconductor laser 34 is a light beam emission source, and irradiates the light beam toward the mirror 13.

  The control circuit 35 monitors the voltage output from the CV conversion circuits 33a and 33b, controls the semiconductor laser 34 based on the voltage value, and controls the drive signal generation circuit 31.

Next, the operation principle of the optical scanning device 1 will be described.
The optical scanning device 1 is a three-degree-of-freedom torsional vibrator having a degree of freedom of twisting with respect to the rotation axes i, j, and k with the support portion 3 as a fixed end.

  A three-degree-of-freedom torsional vibrator theoretically has three vibration modes. That is, the three vibration modes have different resonance frequencies, and the ratio of the angular amplitude of the torsional vibration of each frame to each resonance frequency is different (this is called a vibration mode). Hereinafter, these three vibration modes are referred to as vibration mode 1, vibration mode 2, and vibration mode 3, respectively.

  When a voltage is applied to the comb electrode portions 4a and 4b, an electrostatic force is generated between the comb electrode portions 17 and 19. As will be described in the following detailed description of the vibration mode, since the amplitude of the outer gimbal 11 is smaller than the amplitude of the inner gimbal 12 and the mirror 13, the comb electrode portions 17 and 19 are moved while the outer gimbal 11 vibrates for one cycle. It approaches the comb electrode parts 4a and 4b once. For this reason, if a periodic electrostatic force close to the resonance frequency is applied, the torsional vibrator having three degrees of freedom can be brought into a resonance state (hereinafter, an excitation force for making the resonance state is referred to as a periodic excitation force). Further, every time the comb electrode portions 17 and 19 approach the comb electrode portions 4a and 4b, a periodic excitation force can be applied.

  If a periodic excitation force having a frequency corresponding to each of vibration mode 1, vibration mode 2, and vibration mode 3 is applied, the respective vibration modes can be excited. In addition, if a plurality of periodic excitation forces with a plurality of frequencies are superimposed and applied, a plurality of vibration modes can be excited simultaneously.

Here, for example,
The resonance frequency f1 of vibration mode 1 is 1000 Hz,
The resonance frequency f2 of vibration mode 2 is 5000 Hz,
The resonance frequency f3 of vibration mode 3 is 40000 Hz,
The amplitude ratio r1 of the outer gimbal 11, the inner gimbal 12, and the mirror 13 in the vibration mode 1 is “1: −20: 0.5”,
The amplitude ratio r2 of the outer gimbal 11, the inner gimbal 12, and the mirror 13 in the vibration mode 2 is “1: 0.01: −50”,
The amplitude ratio r3 of the outer gimbal 11, the inner gimbal 12, and the mirror 13 in the vibration mode 3 is “1: 0.02: −0.03”,
The operation of the three-degree-of-freedom torsional vibrator will be described.

  The amplitude ratio in each vibration mode is described in the order of the outer gimbal 11, the inner gimbal 12, and the mirror 13 from the left. For example, when the amplitude of the outer gimbal 11 is “1”, the amplitude ratio r1 indicates that the amplitude of the inner gimbal 12 is “−20” and the amplitude of the mirror 13 is “0.5”.

  In the resonance state of the three-degree-of-freedom torsional vibrator, the phase angle between the frames is theoretically 0 degree or 180 degrees. Therefore, when describing the amplitude ratio, the sign is “+” when the phase angle difference is 0 degree, and the sign is “−” when the difference is 180 degrees. For example, the amplitude ratio r1 indicates that the phase angle difference between the outer gimbal 11 and the mirror 13 is 0 degree, and the phase angle difference between the outer gimbal 11 and the inner gimbal 12 is 180 degrees.

  When the resonance frequency and amplitude ratio of each vibration mode are designed as described above, in the vibration mode 1, mainly the inner gimbal 12 and the mirror 13 connected to the inner gimbal 12 are largely torsionally vibrated at 1000 Hz. Further, in the vibration mode 2, the mirror 13 is largely twisted and vibrated at 5000 Hz.

  For this reason, the laser beam is reflected by the mirror surface portion of the mirror 13 and the vibration mode 1 and the vibration mode 2 are simultaneously excited, so that the vibration mode 2 is in the main scanning direction (5000 Hz) and the vibration mode 1 is in the sub-scanning direction ( 1000 Hz), the laser beam can be scanned two-dimensionally.

Next, the operation of the optical scanning device 1 will be described.
When the drive signal generation circuit 31 outputs the first and second drive signals D1 and D2 based on the control by the control circuit 35, the voltage value of the drive signal is amplified by the amplifier circuit 32 and is applied to the comb electrode portions 4a and 4b. When applied, a pulse voltage is applied between the comb-tooth electrode portions 4a and 4b and the comb-tooth electrode portions 17 and 19, and an electrostatic attractive force that changes periodically is generated. That is, when a voltage is applied between the thin film 22 of the comb electrode portion 4a and the comb electrode portion 17, the comb electrode portion 4a and the comb electrode portion 17 attract each other as shown in FIG. A force for rotating the gimbal 11 in the clockwise direction in FIG. Further, when a voltage is applied between the thin film 22 of the comb electrode part 4b and the comb electrode part 19, the comb electrode part 4b and the comb electrode part 19 attract each other, and the outer gimbal 11 is made opposite to that shown in FIG. A force to rotate in the clockwise direction works. Thereby, the light beam scanning unit 2 reciprocally vibrates about the elastic coupling portions 14a and 14b as the rotation axis i.

  As shown in FIG. 7, the first and second drive signals D1 and D2 output from the drive signal generation circuit 31 are vibration mode resonance frequencies (where the angular amplitude of the mirror 13 is larger than that of the outer gimbal 11 and the inner gimbal 12). The main scanning frequency changes from a low level to a high level. For this reason, the outer gimbal 11 reciprocates at the main scanning frequency (see the waveform W1 in FIG. 7).

  Further, the first and second drive signals D1 and D2 output from the drive signal generation circuit 31 are at a low level at the resonance frequency (sub-scanning frequency) of the vibration mode in which the angular amplitude of the inner gimbal 12 is larger than that of the outer gimbal 11 and the mirror 13. Changes from high to low. For this reason, the outer gimbal 11 vibrates so as to wave at the sub-scanning frequency (see the waveform W2 in FIG. 7).

  As a result, the mirror 13 vibrates at the main scanning frequency with the elastic coupling portions 16a and 16b as the rotation axes, and the inner gimbal 12 vibrates at the sub-scanning frequency with the elastic coupling portions 15a and 15b as the rotation axes.

  In this state, when the mirror 13 is irradiated with a light beam from the semiconductor laser 34, the light beam is emitted by being reflected by the mirror surface of the mirror 13. Scanning is performed in a direction corresponding to the rotation angle.

  On the other hand, with the reciprocal vibration of the outer gimbal 11, the distance between the comb electrode portions 5a and 5b and the comb electrode portions 18 and 20 also periodically changes. Thereby, the electrostatic capacitance between the thin film 22 of the comb-tooth electrode portions 5 a and 5 b and the comb-tooth electrode portions 18 and 20 changes according to the rotation angle of the outer gimbal 11. The control circuit 35 detects the rotation angle of the outer gimbal 11 based on these capacitances. As described above, in the resonance state of the three-degree-of-freedom torsional vibrator, since the phase angle between the frames is theoretically 0 degree or 180 degrees, the mirror is detected by detecting the rotation angle of the outer gimbal 11. Thirteen rotation angles can be detected.

  The optical scanning device 1 configured as described above includes a mirror 13 having a mirror surface portion that reflects a light beam, and elastically deformable elastic connecting portions 16 a and 16 b connected to the mirror 13. An inner gimbal 12 that supports the mirror 13 so as to be swingable about a rotation axis k, and elastically deformable elastic connection portions 15a and 15b connected to the inner gimbal 12, and the elastic connection portions 15a and 15b as rotation axes An outer gimbal 11 that swingably supports the inner gimbal 12 as j, and a support that swingably supports the outer gimbal 11 with the elastically deformable elastic connecting portions 14a and 14b connected to the outer gimbal 11 as the rotation axis i. Part 3, mirror 13, inner gimbal 12, outer gimbal 11, support part 3, elastic coupling parts 16 a and 16 b, elastic coupling parts 15 a and 15 b, and elastic coupling part 14 a, 4b constitute three degrees of freedom coupled vibration system of torsional vibration with a large rotation angle when the specific periodic external force acts.

  Then, the drive signal generation circuit 31 outputs the first and second drive signals D1 and D2 in which the pulse signal that oscillates at the main scanning frequency and the pulse signal that oscillates at the sub-scanning frequency are superimposed, so that the comb electrode portion A periodic excitation force of the main scanning frequency and a periodic excitation force of the sub-scanning frequency are superimposed between the comb-like electrode portions 4a and 4b.

As a result, the mirror 13 vibrates at the main scanning frequency, and the inner gimbal 12 vibrates at the sub-scanning frequency, and the laser light reflected by the mirror 13 can be scanned two-dimensionally.
The drive unit 4 includes a comb electrode portion 4a that applies a specific periodic external force to one side of both sides of the outer gimbal 11 with the rotation axis i interposed therebetween, and a side of the outer gimbal 11 with the rotation axis i interposed therebetween. It is comprised from the comb-tooth electrode part 4b which applies the periodic external force intrinsic | native to the other side.

  Further, the drive signal generation circuit 31 generates a first drive signal D1 for driving the comb-teeth electrode part 4a of the drive unit 4 and a second drive signal D2 for driving the comb-teeth electrode part 4b of the drive unit 4 To do.

  The first drive signal D1 is set to a preset high level so that the voltage becomes higher than the low level from a preset low level so that the voltage becomes 0 V at the main scanning frequency that is the frequency at which the mirror 13 swings. The first main scanning drive signal MS1 having a duty ratio of 50% and the sub-scanning frequency, which is the frequency at which the inner gimbal 12 swings, changes from the low level set in advance so that the voltage becomes higher than 0V. The second drive signal D2 is a signal obtained by multiplying the first sub-scanning drive signal SS1 that changes to a preset high level so as to be higher than the low level and that has a duty of 50%. The second main scanning drive signal MS2 obtained by shifting the phase of the scanning drive signal MS1 by 180 ° is multiplied by the signal obtained by shifting the phase of the first sub-scanning drive signal SS1 by 180 °. This is the second sub-scanning drive signal SS2.

  First, the first drive signal D1 and the second drive signal D2 are signals obtained by multiplying a pulse signal that oscillates at the main scanning frequency by a pulse signal that oscillates at the sub-scanning frequency. For this reason, the comb-tooth electrode portion 4a and the comb-tooth electrode portion 4b are respectively periodically provided on one side and the other side of the outer gimbal 11 across the rotation axis i, corresponding to the vibration mode in which the mirror 13 vibrates at the main scanning frequency. The excitation force and the periodic excitation force corresponding to the vibration mode in which the inner gimbal 12 vibrates at the sub-scanning frequency can be applied in a superimposed manner. Thereby, the mirror 13 vibrates at the main scanning frequency, and the inner gimbal 12 vibrates at the sub-scanning frequency, and the laser light reflected by the mirror 13 can be scanned two-dimensionally. The above-described superimposed periodic excitation force is applied to the outer gimbal 11, so that the outer gimbal 11 reciprocally vibrates at the main scanning frequency with the elastic coupling portions 14a and 14b as the rotation axis i, and the sub scanning. Vibrates like a wave at frequency.

  The first driving signal D1 is a signal obtained by multiplying the first main scanning driving signal MS1 and the first sub scanning driving signal SS1. For this reason, the first drive signal D1 changes from a voltage value of 0V to a predetermined high level higher than 0V (hereinafter referred to as a first drive signal high level) at the main scanning frequency.

  On the other hand, the second drive signal D2 is obtained by shifting the phase of the first main scan drive signal MS1 by 180 ° and the phase of the first sub scan drive signal SS1 by 180 °. This is a signal obtained by multiplying the second sub-scanning drive signal SS2. For this reason, when the voltage of the first drive signal D1 is 0V, the voltage value of the second drive signal D2 becomes a predetermined high level higher than 0V, and the voltage of the first drive signal D1 is higher than 0V. At high level, it becomes 0V.

  Therefore, when the comb electrode portion 4 a applies a periodic excitation force to one side of the outer gimbal 11, the comb electrode portion 4 b does not apply a periodic excitation force to the other side of the outer gimbal 11. Similarly, when the comb electrode part 4 b applies a periodic excitation force to the other side of the outer gimbal 11, the comb electrode part 4 a does not apply a periodic excitation force to one side of the outer gimbal 11.

  For this reason, the comb-tooth electrode part 4a and the comb-tooth electrode part 4b do not apply their own periodic excitation force to the outer gimbal 11 so as to cancel each other's periodic excitation force. Thereby, the vibration amplitude when the outer gimbal 11 reciprocally vibrates at the main scanning frequency with the elastic coupling portions 14a and 14b as the rotation axis i can be increased. In the three-degree-of-freedom coupled vibration system, the vibration amplitude at which the mirror 13 vibrates at the main scanning frequency and the vibration amplitude at which the inner gimbal 12 vibrates at the sub-scanning frequency are proportional to the vibration amplitude of the outer gimbal 11. For this reason, the vibration amplitude at which the mirror 13 vibrates at the main scanning frequency is increased, and the scanning range in the main scanning direction can be increased.

  In the embodiment described above, the mirror 13 is the reflection part in the present invention, the elastic connection parts 16a and 16b are the first elastic connection part in the present invention, and the inner gimbal 12 is the first support part and the elastic connection parts 15a and 15b in the present invention. Is the second elastic connecting portion in the present invention, the outer gimbal 11 is the second supporting portion in the present invention, the elastic connecting portions 14a and 14b are the third elastic connecting portions in the present invention, and the supporting portion 3 is the third supporting portion in the present invention. is there.

  Further, the drive unit 4 is an external force application unit in the present invention, the drive signal generation circuit 31 is a drive signal generation unit in the present invention, the comb electrode unit 4a is a first external force application unit in the present invention, and the comb electrode unit 4b is in the present invention. The second external force application means, the first main scanning drive signal MS1 is the first pulse signal in the present invention, and the first sub-scanning drive signal SS1 is the second pulse signal in the present invention.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, As long as it belongs to the technical scope of this invention, a various form can be taken.
For example, in the above-described embodiment, the outer gimbal 11 is reciprocally vibrated by generating an electrostatic attractive force between the comb-tooth electrode portions 4a and 4b and the comb-tooth electrode portions 17 and 19. However, the outer gimbal 11 may be reciprocally vibrated by piezoelectric driving or the like.

  DESCRIPTION OF SYMBOLS 1 ... Optical scanning device, 2 ... Light beam scanning part, 3 ... Support part, 4 ... Drive part, 4a, 4b ... Comb electrode part, 11 ... Outer gimbal, 12 ... Inner gimbal, 13 ... Mirror, 14a, 14b, 15a, 15b, 16a, 16b ... elastic connecting portion, 17, 19 ... comb electrode portion, 31 ... drive signal generating circuit

Claims (1)

A reflecting portion having a reflecting surface for reflecting the light beam;
A first support part that has an elastically deformable first elastic connection part that is connected to the reflection part, and supports the reflection part in a swingable manner with the first elastic connection part as a first rotation axis;
A second support portion having a second elastic connection portion that is elastically deformable connected to the first support portion, and supports the first support portion in a swingable manner using the second elastic connection portion as a second rotation shaft. When,
A third support portion having a third elastic connection portion that is elastically deformable connected to the second support portion, and supports the second support portion in a swingable manner using the third elastic connection portion as a third rotation shaft. And the reflection part, the first support part, the second support part, the third support part, the first elastic connection part, the second elastic connection part, and the third elastic connection part, A three-degree-of-freedom coupled vibration system that torsionally vibrates at a large rotation angle when an inherent periodic external force is applied,
Furthermore, an external force acting means for causing the inherent periodic external force to act on the three-degree-of-freedom coupled vibration system;
Drive signal generating means for generating a drive signal for driving the external force acting means,
The external force acting means is
A first external force application means for applying the inherent periodic external force to one side of both sides of the second support portion sandwiching the third rotation shaft; and a second support portion sandwiching the third rotation shaft. A second external force application means for applying the inherent periodic external force to the other of the two sides;
The drive signal generating means generates a first drive signal for driving the first external force acting means and a second drive signal for driving the second external force acting means,
The first drive signal is:
A first high level that is preset to be higher than the first low level from a first low level that is preset to be 0 V at a main scanning frequency that is a frequency at which the reflecting portion swings. From the first low pulse level that is set in advance so that the voltage becomes higher than 0 V at the first pulse signal having a duty ratio of 50% and the sub-scanning frequency that is the frequency at which the first support portion swings. , A signal obtained by multiplying a second pulse signal that changes to a second high level that is preset to be higher than the second low level and that has a duty of 50%,
The second drive signal is:
An optical scanning device characterized by being a signal obtained by multiplying a signal obtained by shifting the phase of the first pulse signal by 180 ° and a signal obtained by shifting the phase of the second pulse signal by 180 °.